Protecting device for electric detonators



May 11 1926. 1,583,922

H. L. GRANT PROTECIING DEVICE FOR ELECTRIC DETONATORS Filed Nov. 6, 1924HARRY 1... GRANT,

Patented May 11, 1926.

UNITED STATES 1,583,922 PATENT OFFlC E.

HARRY L. GRANT, OF TAMAQUA, PENNSYLVANIA, ASSIGNOR TO ATLAS IPOYVDERCOMPANY, OF WILMINGTON, DELAWARE, A CORPORATION OF DELAWARE.

PROTECTING DEVICE FOR ELECTRIC DETONATORS.

Application filed November 6, 1924. Serial No. 748,214.

This invention relates to a protecting device for electric detonators.The primary object of the invention is to provide a device of a simpleand inexpensive nature adapted o to be applied tothe lead in wires ofelectric detonators and which will serve, while it is in place, to guardagainst the possibility of the detonator being prematurely exploded byits lead in wires accidentally coming in contact with a source of E. M.F.

The nature and application of the invention will be readily understoodby reference to the accompanying drawing in which:

Figure l is an elevation of an electric detonator and its lead in wires,having the device of the present invention applied thereto, and

Figure 2 is an enlarged sectional view through the safety device orshunt, illustrating its application to the lead in wires.

Like numerals designate corresponding parts in both of the figures ofthe drawing.

Referring to the drawing, 5, designates the casing of an electricdetonator and 6 and 7, the usual lead in wires which extend from saidcasing. In the ordinary use of the detonator, the flow of current ofsufficient strength past point 8 explodes the detonator or blasting 80cap. The lead in wires are insulated for some distance from thedetonator, as indicated at 6, 7 and the ends of the lead in wires areleft bare beyond the point where the insulation terminates, for readyapplication to the firing cable leading from a blasting machine.

In carrying out the invention, the wires 6 and 7 are crossed so thatthey touch each other at a point adjacent the termination of theinsulation 6, 7 and at this oint of contact of the Wires the safetyevice is applied. This device consists of a soft metal body 9,such aslead for example, which may be pressed into firm contact with the wire,and in turn, hold the crossed portions of the wires in intimate contactwith each other. \Vhen this is done the detonator will be effectuallysafeguarded against explosion if the exposed ends of the lead in wiresshould accidentally come in contact with a. source of electrical energy.This is due to the fact that the crossing of the wires and the securingof said wires in intimate contact with each other creates a shortcircuit at that po nt. If the exposed ends of the wires he accidentally,or otherwise, brought into contact with a source of E. M.

F. of sufficient strength,those portions of the wire adjacent the pointof contact may fuse and burn otf, thereby completely disconnect- 6 ingthe detonator from the source of current.

When it is desired to use the detonator the safety device may bestripped therefrom by pulling it longitudinally off the lead in Wires 05and toward the free ends thereof. This action not only removes thesafety device but 'it scrapes and cleans the exposed ends of the wires,leaving them ready for instant attachment to the blasting cable.

Since the insulation 6, 7 extends the entire distance from the safetydevice to the body 5 of the detonator itfollows that contact of a sourceof E. M. F. with that portion of the lead in wires lying between thesafety device and the detonator will not result in the explosion of thedetonator.

The device of the present invention is of utility at all times betweenthe time of manufacture of the detonator and until the same is actuallyexploded on the job but it is of particular utility when the detonatoris be ing transported and while itis being handled about the workpreliminary to the actual firing of a charge. The complete structure ofFig. 1 constitutes a unit as shipped to the trade. In other words, thestructure to be protected prior to its attachment to a main firingcable, comprises a detonator and the two lead wires, the inner portionsof which are covered with insulation and the outer portions of which areleft bare so that the user does not have to expend time in scraping themfree of insulation at the time of use. Therefore, the term lead in wiresas used in the claims, is intended to mean the wires which are combinedwith the individual detonators so that the whole constitutes a unit tobe shipped to the trade.

It will be noted that the lead in wires are 1 in bifilar form whichprevents flow of induced currents. This, in conjunction with thesafeguard afforded by the creation of the short circuit described,renders it certain that the detonator will not be exploded by straycurrents from any source.

It is to be understood that the invention is not limited to anyparticular material for the body 9. It is manifest that any materialwhich will hold the crossed per tions of the wires in intimate contactwith each other will carry out the essential object of the invention,viz, to create an electrical contact atthe point of crossing of saidwires.

However, I prefer to make the shunt from a soft metal such as lead orthe like, in order that the shunt may be pressed firmly around -thewires without injuring them in any manner and also make a more perfectelectrical joint i. e. a joint with little or no contact resistance. Bythe use of a soft metal the shunt may be pressed on the wires firmlyenough to cause it to conform to the shape of the wires where they passthrough it, forming a joint similar to a. soldered joint. This procedureis made possible by the use of a metal which is softer than the metal ofwhich the detonator wires are made. Another advantage of the soft metalshunt is that the user may readily remove it by simply holding the wirewith one hand and pulling it ofl' with the other when ready to fire theshot.

It is to be understood that the invention includes within its purviewwhatever changes fairly come within either the terms or the spirit ofthe appended claims.

Having described my invention, what I claim is:

1. The combination with a detonator and its lead in wires havinginsulation thereon for a portion of their length, of a body embracingsaid wires directly at the termination of said insulation and holdingthem into contact with each other as long as it is in place.

2. The combination with a. detonator and its lead in wires havinginsulation thereon for a portion of their length, of a body embracingthe lead in wires directly at the point of termination of the insulationand holding said wires in crossed and intimate contact with each otheras long as it is in place.

3. A structure as recited in claim 1 where in said body is of materialadapting it to be stripped longitudinally from said wire.

4. The combination with an insulator having lead in wires which areinsulated for a portion of their length, of a soft metal body embracingsaid Wires directly at the point of termination of the insulation andholding said wires in intimate contact with each other.

5. The combination with a detonator and the lead in wires havinginsulation thereon for a portion of their length, of a soft metal bodyembracing said wires directly at the point of termination of theinsulation and holding the said wires in crossed relation at said point,said body being adapted to be stripped longitudinally from said wire.

6. An electrical shunt placed squarely against the insulation of theterminal wires of an electrical detonator,-so as to prevent contact inany manner, of the detonator circuit, with stray electric current orconductors carrying electric current, and so made and applied, that theact of stripping the shunt from the terminal wires cleans the exposedends of the said wires.

7. An electrical detonator in which a shunt made of a metal softer thanthat from which the terminal wires of the detonator are made, is placedsquarely against the insulation of the terminal wires of the saidelectrical detonator.

8. The combination with a detonator, having bifilar lead wires, saidlead wires having a. covering of insulating material thereon for aportion of their length, outwardly, and being bare therebeyond, toprovide means for attachment of the detonator to the common firing cableof a blasting machine, of a body mounted upon and electricallyconnecting said lead wires, so close to the point of termination of theinsulation thereon as to prevent the creation of a short circuit betweenthe point of terminationlof the body and the point of termination of theinsulation, whereby each individual detonator is protected duringshipment and up to the time of use thereof, against accidental explosionunder the influence of stray electric currents.

t In testimony whereof he aflixes his signaure.

HARRY L. GRANT.

